In POS (Point Of Sale) terminals to register and update point of sale information including a trade name, a price, a quantity, time and date, power is under the software control. Except for the purpose of fault tolerance to deal with the case in which power stoppage occurs, and the case in which the main power source is turned OFF by a user, battery driven type POS terminals have been widely used for the purpose of installing a selling space freely in the store or outdoors, are provided with a function to change over the power supplying source from a main power source (a commercial power source) to a battery acting as an auxiliary power source, and can be driven under the circumstances in which power can not be supplied from the main power source.
However, in the conventional battery driven type POS terminals, since it is necessary that the POS terminal main body is connected to the main power source to thereby charge the battery, or the battery is charged with an exclusive battery charger after the battery is taken out from the inside of the POS terminal, the work burden in charging the battery was large, particularly in case that the POS terminal is installed at a position distant from the main power source.